1. Field of the Invention
The present invention relates to retroviral protease inhibitors and, more particularly, relates to novel compounds and a composition and method for inhibiting retroviral proteases. This invention, in particular, relates to sulfonamide-containing hydroxyethylamine protease inhibitor compounds, a composition and method for inhibiting retroviral proteases such as human immunodeficiency virus (HIV) protease and for treating a retroviral infection, e.g., an HIV infection. The subject invention also relates to processes for making such compounds as well as to intermediates useful in such processes.
2. Related Art
During the replication cycle of retroviruses, gag and gag-pol gene products are translated as proteins. These proteins are subsequently processed by a virally encoded protease (or proteinase) to yield viral enzymes and structural proteins of the virus core. Most commonly, the gag precursor proteins are processed into the core proteins and the pol precursor proteins are processed into the viral enzymes, e.g., reverse transcriptase and retroviral protease. It has been shown that correct processing of the precursor proteins by the retroviral protease is necessary for assembly of infectious virons. For example, it has been shown that frameshift mutations in the protease region of the pol gene of HIV prevents processing of the gag precursor protein. It has also been shown through site-directed mutagenesis of an aspartic acid residue in the HIV protease that processing of the gag precursor protein is prevented. Thus, attempts have been made to inhibit viral replication by inhibiting the action of retroviral proteases.
Retroviral protease inhibition may involve a transition-state mimetic whereby the retroviral protease is exposed to a mimetic compound which binds to the enzyme in competition with the gag and gag-pol proteins to thereby inhibit replication of structural proteins and, more importantly, the retroviral protease itself. In this manner, retroviral replication proteases can be effectively inhibited.
Several classes of compounds have been proposed, particularly for inhibition of proteases, such as for inhibition of HIV protease. Such compounds include hydroxyethylamine isosteres and reduced amide isosteres. See, for example, EP O 346 847; EP O 342,541; Roberts et al, xe2x80x9cRational Design of Peptide-Based Proteinase Inhibitors,xe2x80x9d Science 248, 358 (1990); and Erickson et al, xe2x80x9cDesign Activity, and 2.8 xc3x85 Crystal Structure of a C2 Symmetric Inhibitor Complexed to HIV-1 Protease,xe2x80x9d Science, 249, 527 (1990).
Several classes of compounds are known to be useful as inhibitors of the proteolytic enzyme renin. See, for example, U.S. Pat. No. 4,599,198; U.K. 2,184,730; G.B. 2,209,752; EP O 264 795; G.B. 2,200,115 and U.S. SIR H725. Of these, G.B. 2,200;115, GB 2,209,752, EP O 264,795, U.S. SIR H725 and U.S. Pat. No. 4,599,198 disclose urea-containing hydroxyethylamine renin inhibitors. G.B. 2,200,115 also disclose certain sulfamoyl-containing hydroxyethylamine renin inhibitors. EP O 264 795 also discloses certain sulfonamide-containing renin inhibitor compounds. However, it is known that, although renin and HIV proteases are both classified as aspartyl proteases, compounds which are effective renin inhibitors generally cannot be predicted to be effective HIV protease inhibitors.
The present invention is directed to virus inhibiting compounds and compositions. More particularly, the present invention is directed to retroviral protease inhibiting compounds and compositions, to a method of inhibiting retroviral proteases, to processes for preparing the compounds and to intermediates useful in such processes. The subject compounds are characterized as succinoylamino hydroxyethylamino sulfonamide inhibitor compounds.
In accordance with the present invention, there is provided a retroviral protease inhibiting compound of the formula: 
or a pharmaceutically acceptable salt, prodrug or ester thereof wherein:
x represents 0, 1 or 2;
t represents either 0 or 1;
R1 represents hydrogen, xe2x80x94CH2SO2NH2, xe2x80x94CO2CH3, xe2x80x94CONHCH3, xe2x80x94CON(CH3)2, xe2x80x94CH2C(O)NHCH3, xe2x80x94CH2C(O)N(CH3)2, xe2x80x94CONH2, xe2x80x94C(CH3)2(SH)xe2x80x94C(CH3)2(SCH3), xe2x80x94C(CH3)2(S[O]CH3), xe2x80x94C(CH3)2(S[O]2CH3), alkyl, haloalkyl, alkenyl, alkynyl and cycloalkyl radicals and amino acid side chains selected from asparagine, S-methyl cysteine and the corresponding sulfoxide and sulfone derivatives thereof, glycine, leucine, isoleucine, allo-isoleucine, tert-leucine, phenylalanine, ornithine, alanine, histidine, norleucine, glutamine, valine, threonine, serine, o-alkyl serine, aspartic acid, beta-cyano alanine, and allothreonine side chains;
R2 represents alkyl, aryl, cycloalkyl, cycloalkylalkyl and aralkyl radicals, which radicals are optionally substituted with a group selected from alkyl and halogen radicals, and xe2x80x94NO2, xe2x80x94Cxe2x89xa1N, CF3, xe2x80x94OR9, xe2x80x94SR9 wherein R9 represents hydrogen and alkyl radicals;
R3 represents hydrogen, alkyl, haloalkyl, alkenyl, alkynyl, hydroxyalkyl, alkoxyalkyl, cycloalkyl, cycloalkylalkyl, heterocycloalkyl, heteroaryl, heterocycloalkylalkyl, aryl, aralkyl, heteroaralkyl, aminoalkyl and mono- and disubstituted aminoalkyl radicals, wherein said substituents are selected from alkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl, heteroaryl, heteroaralkyl, heterocycloalkyl, and heterocycloalkylalkyl radicals, or in the case of a disubstituted aminoalkyl radical, said substituents along with the nitrogen atom to which they are attached, form a heterocycloalkyl or a heteroaryl radical;
Xxe2x80x2 represents N, O and C(R17) where R17 represents hydrogen and alkyl radicals;
Y and Yxe2x80x2 independently represent O,S and NR15 wherein R15 represents hydrogen and radicals as defined for R3;
R4 represents radicals as defined by R3 except for hydrogen;
R6 represents hydrogen and alkyl radicals as defined for R3;
R30, R31 and R32 represent radicals as defined for R1, or one of R1 and R30 together with one of R31 and R32 and the carbon atoms to which they are attached form a cycloalkyl radical; and
R33 and R34 independently represent hydrogen, radicals as defined for R3 or R33 and R34 together with Xxe2x80x2 represent cycloalkyl, aryl, heterocyclyl and heteroaryl radicals, provided that when Xxe2x80x2 is O; R34 is absent.
A preferred class of retroviral inhibitor compounds of the present invention are those represented by the formula: 
or a pharmaceutically acceptable salt, prodrug or ester thereof, preferably wherein the absolute stereochemistry about the hydroxy group is designated as (R);
R1 represents hydrogen, xe2x80x94CH2SO2NH2, xe2x80x94CO2CH3, xe2x80x94CONHCH3, xe2x80x94CON(CH3)2, xe2x80x94CH2C(O)NHCH3, xe2x80x94CH2C(O)N(CH3)2, xe2x80x94CONH2, xe2x80x94C(CH3)2(SCH3), xe2x80x94C(CH3)2(S[O]CH3), xe2x80x94C(CH3)2(S[O]2CH3), alkyl, haloalkyl, alkenyl, alkynyl and cycloalkyl radicals and amino acid side chains selected from asparagine, S-methyl cysteine and the corresponding sulfoxide and sulfone derivatives thereof, glycine, leucine, isoleucine, allo-isoleucine, tert-leucine, phenylalanine, ornithine, alanine, histidine, norleucine, glutamine, valine, threonine, serine, aspartic acid, beta-cyano alanine, and allothreonine side chains;
R2 represents alkyl, aryl, cycloalkyl, cycloalkylalkyl, and aralkyl radicals, which radicals are optionally substituted with a group selected from alkyl and halogen radicals, NO2, xe2x80x94Cxe2x89xa1N, CF3, OR9 and SR9 wherein R9 represents hydrogen and alkyl radicals;
R3 represents hydrogen, alkyl, haloalkyl, alkenyl, alkynyl, hydroxyalkyl, alkoxyalkyl, cycloalkyl, cycloalkylalkyl, heterocycloalkyl, heteroaryl, heterocycloalkylalkyl, aryl, aralkyl, heteroaralkyl, aminoalkyl and mono- and disubstituted aminoalkyl radicals, wherein said substituents are selected from alkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl, heteroaryl, heteroaralkyl, heterocycloalkyl, and heterocycloalkylalkyl radicals, or in the case of a disubstituted aminoalkyl radical, said substituents along with the nitrogen atom to which they are attached, form a heterocycloalkyl or a heteroaryl radical;
R4 represents radicals as defined by R3 except for hydrogen;
R30, R31 and R32 represent radicals as defined for R1, or one of R1 and R30 together with one of R31 and R32 and the carbon atoms to which they are attached form a cycloalkyl radical; and
R33 and R34 independently represent hydrogen, radicals as defined for R3 or R33 and R34 together with the nitrogen atom to which they are attached represent heterocycloalkyl and heteroaryl radicals;
Y and Yxe2x80x2 independently represent O, S and NR15 wherein R15 represents hydrogen and radicals as defined for R3, Preferably, Y and Yxe2x80x2 represent O.
Yet another preferred class of compounds are those represented by the formula: 
or a pharmaceutically acceptable salt, prodrug or ester thereof, preferably-wherein the stereochemistry about the hydroxy group is designated as R, wherein Y, Yxe2x80x2, R1, R2, R3, R4, R30, R31 and R32 are as defined above with respect to Formula (II). Preferably, Y and Yxe2x80x2 represent O.
As utilized herein, the term xe2x80x9calkylxe2x80x9d, alone or in combination, means a straight-chain or branched-chain alkyl radical containing from 1 to about 10, preferably from 1 to about 8, carbon atoms. Examples of such radicals include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, iso-amyl, hexyl, octyl and the like. The term xe2x80x9calkenylxe2x80x9d, alone or in combination, means a straight-chain or branched-chain hydrocarbon radial having one or more double bonds and containing from 2 to about 18 carbon atoms preferably from 2 to about 8 carbon atoms. Examples of suitable alkenyl radicals include ethenyl, propenyl, 1,4-butadienyl and the like. The term alkynyl, alone or in combination, means a straight-chain hydrocarbon radical having one or more triple bonds and containing from 2 to about 10 carbon atoms. Examples of alkynyl radicals include ethynyl, propynyl, propargyl and the like. The term xe2x80x9calkoxyxe2x80x9d, alone or in combination, means an alkyl ether radical wherein the term alkyl is as defined above. Examples of suitable alkyl ether radicals include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, iso-butoxy, sec-butoxy, tert-butoxy and the like. The term xe2x80x9ccycloalkylxe2x80x9d, alone or in combination, means a saturated or partially saturated monocyclic, bicyclic or tricyclic alkyl radical wherein each cyclic moiety contains from about 3 to about 8 carbon atoms. The term xe2x80x9ccycloalkylalkylxe2x80x9d means an alkyl radical as defined above which is substituted by a cycloalkyl radical containing from about 3 to about 8, preferably from about 3 to about 6, carbon atoms. Examples of such cycloalkyl radicals include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and the like. The term xe2x80x9carylxe2x80x9d, alone or in combination, means a phenyl or naphthyl radical which optionally carries one or more substituents selected from alkyl, alkoxy, halogen, hydroxy, amino, nitro, cyano, haloalkyl and the like, such as phenyl, p-tolyl, 4-methoxyphenyl, 4-(tert-butoxy)phenyl, 4-fluorophenyl, 4-chlorophenyl, 4-hydroxyphenyl, 1-naphthyl, 2-naphthyl, and the like. The term xe2x80x9caralkylxe2x80x9d, alone or in combination, means an alkyl radical as defined above in which one hydrogen atom is replaced by an aryl radical as defined above, such as benzyl, 2-phenylethyl and the like. The term xe2x80x9caralkoxy carbonylxe2x80x9d, alone or in combination, means a radical of the formula xe2x80x94C(O)xe2x80x94O-aralkyl in which the term xe2x80x9caralkylxe2x80x9d has the significance given above. An example of an aralkoxycarbonyl radical is benzyloxycarbonyl. The term xe2x80x9caryloxyxe2x80x9d means a radical of the formula aryl-Oxe2x80x94 in which the term aryl has the significance given above. The term xe2x80x9calkanoylxe2x80x9d, alone or in combination, means an acyl radical derived from an alkanecarboxylic acid, examples of which include acetyl, propionyl, butyryl, valeryl, 4-methylvaleryl, and the like. The term xe2x80x9ccycloalkylcarbonylxe2x80x9d means an acyl group derived from a monocyclic or bridged cycloalkanecarboxylic acid such as cyclopropanecarbonyl; cyclohexanecarbonyl, adamantanecarbonyl, and the like, or from a benz-fused monocyclic cycloalkanecarboxylic acid which is optionally substituted by, for example, alkanoylamino, such as 1,2,3,4-tetrahydro-2-naphthoyl, 2-acetamido-1,2,3,4-tetrahydro-2-naphthoyl. The term xe2x80x9caralkanoylxe2x80x9d means an acyl radical derived from an aryl-substituted alkanecarboxylic acid such as phenylacetyl, 3-phenylpropionyl (hydrocinnamoyl), 4-phenylbutyryl, (2-naphthyl)acetyl, 4-chlorohydrocinnamoyl, 4-aminohydrocinnamoyl,4-methoxyhydrocinnamoyl, and the like. The term xe2x80x9caroylxe2x80x9d means an acyl radical derived from an aromatic carboxylic acid. Examples of such radicals include aromatic carboxylic acids, an optionally substituted benzoic or naphthoic acid such as benzoyl, 4-chlorobenzoyl, 4-carboxybenzoyl, 4-(benzyloxycarbonyl)benzoyl, 1-naphthoyl, 2-naphthoyl, 6-carboxy-2 naphthoyl, 6-(benzyloxycarbonyl)-2-naphthoyl, 3-benzyloxy-2-naphthoyl, 3-hydroxy-2-naphthoyl, 3-(benzyloxyformamido)-2-naphthoyl, and the like. The heterocyclyl or heterocycloalkyl portion of a heterocyclylcarbonyl, heterocyclyloxycarbonyl, heterocyclylalkoxycarbonyl, or heterocyclyalkyl group or the like is a saturated or partially unsaturated monocyclic, bicyclic or tricyclic heterocycle which contains one or more hetero atoms selected from nitrogen, oxygen and sulphur, which is optionally substituted on one or more carbon atoms by halogen, alkyl, alkoxy, oxo, and the like, and/or on a secondary nitrogen atom (i.e., xe2x80x94NHxe2x80x94) by alkyl, aralkoxycarbonyl, alkanoyl, phenyl or phenylalkyl or on a tertiary nitrogen atom (i.e. xe2x95x90Nxe2x80x94) by oxido and which is attached via a carbon atom. The heteroaryl portion of a heteroaroyl, heteroaryloxycarbonyl, or a heteroaralkoxy carbonyl group or the like is an aromatic monocyclic, bicyclic, or tricyclic heterocycle which contains the hetero atoms and is optionally substituted as defined above with respect to the definition of heterocyclyl. Examples of such heterocyclyl and heteroaryl groups are pyrrolidinyl, piperidinyl, piperazinyl, morpholinyl, thiamorpholinyl, pyrrolyl, imidazolyl (e.g., imidazol 4-yl, 1-benzyloxycarbonylimidazol-4-yl, etc.), pyrazolyl, pyridyl, pyrazinyl, pyrimidinyl, furyl, thienyl, triazolyl, oxazolyl, thiazolyl, indolyl (e.g., 2-indolyl, etc.), quinolinyl, (e.g., 2-quinolinyl, 3-quinolinyl, 1-oxido-2-quinolinyl, etc.), isoquinolinyl (e.g., 1-isoquinolinyl, 3-isoquinolinyl, etc.), tetrahydroquinolinyl (e.g., 1,2,3,4-tetrahydro-2-quinolyl, etc.), 1,2,3,4-tetrahydroisoquinolinyl (e.g., 1,2,3,4-tetrahydro-1-oxo-isoquinolinyl, etc.), quinoxalinyl, xcex2-carbolinyl, 2-benzofurancarbonyl, 1-,2-,4- or 5-benzimidazolyl, and the like. The term xe2x80x9ccycloalkylalkoxycarbonylxe2x80x9d means an acyl group derived from a cycloalkylalkoxycarboxylic acid of the formula cycloalkylalkyl-Oxe2x80x94COOH wherein cycloalkylalkyl has the significance given above. The term xe2x80x9caryloxyalkanoylxe2x80x9d means an acyl radical of the formula aryl-O-alkanoyl wherein aryl and alkanoyl have the significance given above. The term xe2x80x9cheterocyclyloxycarbonylxe2x80x9d means an acyl group derived from heterocyclyl-Oxe2x80x94COOH wherein heterocyclyl is as defined above. The term xe2x80x9cheterocyclylalkanoylxe2x80x9d is an acyl radical derived from a heterocyclyl-substituted alkane carboxylic acid wherein heterocyclyl has the significance given above. The term xe2x80x9cheterocyclylalkoxycarbonylxe2x80x9d means an acyl radical derived from a heterocyclyl-substituted alkane-Oxe2x80x94COOH wherein heterocyclyl has the significance given above. The term xe2x80x9cheteroaryloxycarbonylxe2x80x9d means an acyl radical derived from a carboxylic acid represented by heteroaryl-Oxe2x80x94COOH wherein heteroaryl has the significance given above. The term xe2x80x9caminocarbonylxe2x80x9d alone or in combination, means an amino-substituted carbonyl (carbamoyl) group derived from an amino-substituted carboxylic acid wherein the amino group can be a primary, secondary or tertiary amino group containing substituents selected from hydrogen, and alkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl radicals and the like. The term xe2x80x9caminoalkanoylxe2x80x9d means an acyl group derived from an amino-substituted alkanecarboxylic acid wherein the amino group can be a primary, secondary or tertiary amino group containing substituents selected from hydrogen, and alkyl, aryl, aralkyl, cycloalkyl, cycloalkylalkyl radicals and the like. The term xe2x80x9chalogensxe2x80x9d means fluorine, chlorine, bromine or iodine. The term xe2x80x9cleaving groupxe2x80x9d generally refers to groups readily displaceable by a nucleophile, such as an amine, a thiol or an alcohol nucleophile. Such leaving groups are well known in the art. Examples of such leaving groups include N-hydroxysuccinimide, N-hydroxybenzotriazole, halides, triflates, tosylates and the like. Preferred leaving groups are indicated herein where appropriate.
Procedures for preparing the compounds of Formula I are set forth below. It should be noted that the general procedure is shown as it relates to preparation of compounds having the specified stereochemistry, for example, wherein the absolute stereochemistry about the hydroxyl group is designated as (R). However, such procedures are generally applicable, to those compounds of opposite configuration, e.g., where the stereochemistry about the hydroxyl group is (S). In addition, the compounds having the (R) stereochemistry can be utilized to produce those having the (S) stereochemistry. For example, a compound having the (R) stereochemistry can be inverted to the (S) stereochemistry using well-known methods.
The compounds of the present invention represented by Formula I above can be prepared utilizing the following general procedure. An N-protected chloroketone derivative of an amino acid having the formula: 
wherein P represents an amino protecting group, and R2 is as defined above, is reduced to the corresponding alcohol utilizing an appropriate reducing agent. Suitable amino protecting groups are well known in the art and include carbobenzoxy, butyryl, t-butoxycarbonyl, acetyl, benzoyl and the like. A preferred amino protecting group is carbobenzoxy. A preferred N-protected chloroketone is N-benzyloxycarbonyl-L-phenylalanine chloromethyl ketone. A preferred reducing agent is sodium borohydride. The reduction reaction is conducted at a temperature of from xe2x88x9210xc2x0 C. to about 25xc2x0 C., preferably at about 0xc2x0 C., in a suitable solvent system such as, for example, tetrahydrofuran, and the like. The N-protected chloroketones are commercially available e.g. such as from Bachem, Inc., Torrance, Calif. Alternatively, the chloroketones can be prepared by the procedure set forth in S. J. Fittkau, J. Prakt. Chem., 315, 1037 (1973), and subsequently N-protected utilizing procedures which are well known in the art.
The halo alcohol can be used directly, as described below, or, preferably, is then reacted, preferably at room temperature, with a suitable base in a suitable solvent system to produce an N-protected amino epoxide of the formula: 
wherein P and R2 are as defined above. Suitable solvent systems for preparing the amino epoxide include ethanol, methanol, isopropanol, tetrahydrofuran, dioxane, and the like including mixtures thereof. Suitable bases for producing the epoxide from the reduced chloroketone include potassium hydroxide, sodium hydroxide, potassium t-butoxide, DBU and the like. A preferred base is potassium hydroxide.
Alternatively, a protected amino epoxide can be prepared starting with an L-amino acid which is reacted with a suitable amino-protecting group in a suitable solvent to produce an amino-protected L-amino acid ester of the formula: 
wherein P1 and p2 independently represent hydrogen, benzyl and amino-protecting groups as defined above with respect to P, provided that P1 and p2 are not both hydrogen; p3 represents a carboxyl protecting group such as methyl, ethyl, tertiary-butyl, benzyl, and the like, and R2 is as defined above.
The amino-protected L-amino acid ester is then reduced, to the corresponding alcohol. For example, the amino-protected L-amino acid ester can be reduced with diisobutylaluminum hydride at xe2x88x9278xc2x0 C. in a suitable solvent such as toluene. The resulting alcohol is then converted, for example, by way of a Swern oxidation, to the corresponding aldehyde of the formula: 
wherein p1, p2 and R2 are as defined above. Thus, a dichloromethane solution of the alcohol is added to a cooled (xe2x88x9275 to xe2x88x9268xc2x0 C.) solution of oxalyl chloride in dichloromethane and DMSO in dichloromethane and stirred for 35 minutes.
The aldehyde resulting from the Swern oxidation is then reacted with a halomethyllithium reagent, which reagent is generated in situ by reacting an alkyllithium or arylithium compound with a dihalomethane represented by the formula X1CH2X2 wherein X1 and X2 independently represent I, Br or Cl. For example, a solution of the aldehyde and chloroiodomethane in THF is cooled to xe2x88x9278xc2x0 C. and a solution of n-butyllithium in hexane is added. The resulting product is a mixture of diastereomers of the corresponding amino-protected epoxides of the formulas: 
The diastereomers can be separated, e.g., by chromatography or, alternatively, once reacted in subsequent steps the diastereomeric products can be separated. For compounds having the (S) stereochemistry, a D-amino acid can be utilized in place of the L-amino acid.
The amino epoxide is then reacted, in a suitable solvent system, with an equal amount, or preferably an excess of, a desired amine of the formula:
R3NH2
wherein R3 is hydrogen or is as defined above. The reaction can be conducted over a wide range of temperatures, e.g., from about 10xc2x0 C. to about 100xc2x0 C., but is preferably, but not necessarily, conducted at a temperature at which the solvent begins to reflux. Suitable solvent systems include protic, non-protic and dipolar aprotic solvents, such as, for example, those wherein the solvent is an alcohol, such as methanol, ethanol, isopropanol, and the like, ethers such as tetrahydrofuran, dioxane and the like, and toluene, N,N-dimethylformamide, dimethyl sulfoxide, and mixtures thereof. A preferred solvent is isopropanol. Exemplary amines corresponding to the formula R3NH2 include benzyl amine, isobutylamine, n-butyl amine, isopentyl amine, isoamylamine, cyclohexanemethyl amine, naphthylene methyl amine and the like. The resulting product is a 3-(N-protected amino)-3-(R2)-1-(NHR3)-propan-2-ol derivative (hereinafter referred to as an amino alcohol) can be represented by the formulas: 
wherein p, p1, p2, R2 and R3 are as described above. Alternatively, a haloalcohol can be utilized in place of the amino epoxide.
The amino alcohol defined above is then reacted in a suitable solvent with a sulfonyl chloride (R4SO2Cl) or sulfonyl anhydride in the presence of an acid scavenger. Suitable solvents in which the reaction can be conducted include methylene chloride, tetrahydrofaran and the like. Suitable acid scavangers include triethylamine, pyridine and the like. Preferred sulfonyl chlorides are methanesulfonyl chloride and benzenesulfonyl chloride. The resulting sulfonamide derivative can be represented, depending on the epoxide utilized by the formulas: 
wherein p, p1, p2, R2, R3 and R4 are as defined above.
The sulfonyl halides of the formula R4SO2X can be prepared by the reaction of a suitable Grignard or alkyl lithium reagent with sulfuryl chloride, or sulfur dioxide followed by oxidation with a halogen, preferably chlorine. Also, thiols may be oxidized to sulfonyl chlorides using chlorine in the presence of water under carefully controlled conditions. Additionally, sulfonic acids may be converted to sulfonyl halides using reagents such as PCl5, and also to anhydrides using suitable dehydrating reagents. The sulfonic acids may in turn be prepared using procedures well known in the art. Such sulfonic acids are also commercially available.
In place of the sulfonyl halides, sulfinyl halides (R4SOX) or sulfenyl halides (R4SX) can be utilized to prepare compounds wherein the xe2x80x94SO2xe2x80x94 moiety is replaced by an xe2x80x94SOxe2x80x94 or xe2x80x94Sxe2x80x94 moiety, respectively.
Following preparation of the sulfonamide derivative, the amino protecting group P or P1 and P2 is removed under conditions which will not affect the remaining portion of the molecule. These methods are well known in the art and include acid hydrolysis, hydrogenolysis and the like. A preferred method involves removal of the protecting group, e.g., removal of a carbobenzoxy group, by hydrogenolysis utilizing palladium on carbon in a suitable solvent system such as an alcohol, acetic acid, and the like or mixtures thereof. Where the protecting group is a t-butoxycarbonyl group, it can be removed utilizing an inorganic or organic acid, e.g., HCl or trifluoroacetic acid, in a suitable solvent system, e.g., dioxane or methylene chloride. The resulting product is the amine salt derivative. Where the protecting group is a benzyl radical, it can be removed by hydrogenolysis. Following neutralization of the salt, the amine is then reacted with a succinic acid as described below.
To produce the succinic acid portion of the compounds of Formula I, the starting material is a lactate of the formula: 
wherein Pxe2x80x3 represents alkyl and aralkyl radicals, such as, for example, ethyl, methyl, benzyl and the like. The hydroxyl group of the lactate is protected as its ketal by reaction in a suitable solvent system with methyl iso-propenyl ether (1,2-methoxypropene) in the presence of a suitable acid. Suitable solvent systems include methylene chloride, tetrahydrofuran and the like as well as mixtures thereof. Suitable acids include POCl3 and the like. It should be noted that well-known groups other than methyl isopropenyl ether can be utilized to form the ketal. The ketal is then reduced with diisobutylaluminum hydride (DIBAL) at xe2x88x9278xc2x0 C. to produce the corresponding aldehyde which is then treated with ethylidene triphenylphosphorane (Wittig reaction) to produce a compound represented by the formula: 
The ketal protecting group is then removed utilizing procedures well-known in the art such as by mild acid hydrolysis. The resulting compound is then esterified with isobutyryl chloride to produce a compound of the formula: 
This compound is then treated with lithium diisopropyl amide at xe2x88x9278xc2x0 C. followed by warming of the reaction mixture to room temperature to effect a Claisen rearrangement ([3,3]) to produce the corresponding acid represented by the formula: 
Those skilled in the art will recognize that variations on this scheme are possible, using either different protecting groups or reagents to carry out the same transformations. One can also utilize other acid chlorides in place of isobutyryl chloride to prepare similar analogs.
Treatment of the acid with benzyl bromide in the presence of a tertiary amine base, e.g., DBU, produces the corresponding ester which is then cleaved oxidatively to give a trisubstituted succinic acid: 
The trisubstituted succinic acid is then coupled to the sulfonamide isostere utilizing procedures well known in the art. To produce the free acid, the benzyl ester is removed by hydrogenolysis to produce the corresponding acid. The acid can then be converted to the primary amide by methods well-known in the art. The resulting product is a compound represented by Formula I.
An alternative method for preparing trisubstituted succinic acids involves reacting an ester of acetoacetic acid represented by the formula: 
where R is a suitable protecting group, such as methyl, ethyl, benzyl or t-butyl with sodium hydride and a hydrocarbyl halide (R31X or R32X) in a suitable solvent, e.g., THF, to produce the corresponding disubstituted derivative represented by the formula: 
This disubstituted acetoacetic acid derivative is then treated with lithium diisopropyl amide at about xe2x88x9210xc2x0 C. and in the presence of PhN(triflate)2 to produce a vinyl triflate of the formula: 
The vinyl triflate is then carbonylated utilizing a palladium catalyst, e.g., Pd(OAc)2 and Ph3P, in the presence of an alcohol (Rxe2x80x3OH) or water (Rxe2x80x3=H) and a base, e.g., triethylamine, in a suitable solvent such as DMF, to produce the olefinic ester or acid of the formula: 
The olefin can then be subsequently asymmetrically hydrogenated, as described below, to produce a trisubstituted succinic acid derivative of the formula: 
If Rxe2x80x3 is not H, Rxe2x80x3 can be removed by either hydrolysis, acidolysis, or hydrogenolysis, to afford the corresponding acid, which is then coupled to the sulfonamide isostere as described above and then, optionally, the R group removed to produce the corresponding acid, and optionally, converted to the amide.
Alternatively, one can react the sulfonamide isostere with either a suitably monoprotected succinic acid or glutaric acid of the following structure; 
followed by removal of the protecting group and conversion of the resulting acid to an amide. One can also react an anhydride of the following structure; 
with the sulfonamide isostere and then separate any isomers or convert the resulting acid to an amide and then separate any isomers.
It is contemplated that for preparing compounds of the Formulas having R6, the compounds can be prepared following the procedure set forth above and, prior to coupling the sufonamide derivative to the succinic acid portion of the molecule carried through a procedure referred to in the art as reductive amination. Thus, a sodium cyanoborohydride and an appropriate aldehyde or ketone can be reacted with the sulfonamide derivative compound or appropriate analog at room temperature in order to reductively aminate any of the compounds of Formulas I-III. It is also contemplated that where R3 of the amino alcohol intermediate is hydrogen, the inhibitor compounds can be prepared through reductive amination of the final product of the reaction between the amino alcohol and the amine or at any other stage of the synthesis for preparing the inhibitor compounds.
Contemplated equivalents of the general formulas set forth above for the antiviral compounds and derivatives as well as the intermediates are compounds otherwise corresponding thereto and having the same general properties wherein one or more of the various R groups are simple variations of the substituents as defined therein, e.g., wherein R is a higher alkyl group than that indicated. In addition, where a substituent is designated as, or can be, a hydrogen, the exact chemical nature of a substituent which is other than hydrogen at that position, e.g., a hydrocarbyl radical or a halogen, hydroxy, amino and the like functional group, is not critical so long as it does not adversely affect the overall activity and/or synthesis procedure.
The chemical reactions described above are generally disclosed in terms of their broadest application to the preparation of the compounds of this invention. Occasionally, the reactions may not be applicable as described to each compound included within the disclosed scope. The compounds for which this occurs will be readily recognized by those skilled in the art. In all such cases, either the reactions can be successfully performed by conventional modifications known to those skilled in the art, e.g., by appropriate protection of interfering groups, by changing to alternative conventional reagents, by routine modification of reaction conditions, and the like, or other reactions disclosed herein or otherwise conventional, will be applicable to the preparation of the corresponding compounds of this invention. In all preparative methods, all starting materials are known or readily preparable from known starting materials.
Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The following preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.
All reagents were used as received without purification. All proton and carbon NMR spectra were obtained on either a Varian VXR-300 or VXR-400 nuclear magnetic resonance spectrometer.